Browsing by Author "King, Michael"

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    The influence of methylphenidate on heart rate and brain connectivity
    (2018) Van Breda, Keelyn; Rauch, Laurie; Stein, Dan J; King, Michael; Jankiewicz, Marcin
    The central governor model (CGM) proposes that muscle recruitment is regulated by the brain through subconscious homeostatic control of afferent feedback. It has been suggested that the dopaminergic system plays a key role in the CGM, with dopaminergic activation leading to lower fatigue thresholds. Key neural circuits, including the central autonomic network (CAN), may also play a role in altering thresholds by reducing conscious bodily awareness, known as interoception. However, few studies have directly examined the dopaminergic neurotransmitter system and CAN connectivity, during exercise-induced fatigue. Although there is reason to suspect that subjects with high activity (HA) and low activity (LA) levels have different fatigue thresholds, potential differences in dopaminergic function and related circuity have not been compared across these groups. In this thesis, I was therefore interested in examining the impact of a dopaminergic agent, methylphenidate (MPH) on: a) brain connectivity at rest before exercise and during exercise, b) on heart rate (HR) at rest before exercise and during exercise. Furthermore, c) I was interested in whether the effect of MPH administration (MA) on HR and functional connectivity (FC), between CAN regions, pre-exercise impacted HR and FC during exercise and whether this differed between HA and LA subjects. In order to measure the effect of MA on brain connectivity at rest and during exercise I used a functional magnetic resonance imaging (fMRI) scanner. To measure the effect of MA on fatigue thresholds, I used a MRI compatible handgrip device which recorded grip force output during a fatiguing handgrip task. To measure HR before and during handgrip exercise I used a MRI compatible electrocardiogram (ECG) machine. My first study aimed to determine the effect of MA on resting state (R-fMRI) FC between CAN regions and its correlation with HR before exercise. My second study aimed to see the effect of MA on task HR, force output and, FC and EC between CAN regions, during a fatiguing handgrip task. My third study aimed to see the effect of MA on the relationship between HR and FC pre-exercise and HR and FC during exercise and whether this differed between LA and HA subjects. I found that: 1.) MA decreased R-fMRI FC between CAN regions, and that this was associated with an increase in HR during resting state 2.) MA decreased FC between CAN regions with an associated increase in task HR and force output during a fatiguing handgrip task 3.) After MA, R-fMRI FC determines task FC independent of HR 4.) MA significantly increased task HR in LA but not HA subjects 5.) After MA, R-fMRI FC determines task FC independent of HR in LA but not HA subjects. Taken together, the functional uncoupling of CAN regions and increased HR after MA suggests that MA increases the fatigue threshold by diverting attention away from interoceptive cues, such as HR. However, this finding may be more relevant in LA subjects, where MA is also associated with increased HR during exercise.
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    A study of the development of the structures and themes in the short stories of Nadine Gordimer
    (1984) King, Michael; Haresnape, Geoffrey
    Most current studies of Gordimer concern themselves with her novels, and her short stories have not received significant critical attention as stories in their own right, worthy of study both for their structural and formal qualities, and for the contribution they make as social, political and historical comment on their time. This study begins with a general discussion of the artistic demands of the modern short story, and then proceeds to a close study of all Gordimer's published short stories, concentrating on the developments that occur in the characteristic structures and themes of her stories. Each of her collections is dealt with, chronologically, in a separate chapter. In the course of the study, it became clear that two critical approaches were needed in order to explain satisfactorily developments of structure on the one hand, and theme on the other. The basic approach has been close textual reading, which has been enhanced especially after her fifth collection by consideration of the stories' socio-historical dimensions as well. Gordimer's early stories deal with what are later seen to be characteristic themes, race and racial differences, self-deception, illusion, or the stripping away of illusions, turning points in childhood and marriage. Later stories show the developments in these thematic areas, most notably in the field of race. Other stories reveal a growing interest in the role and position of women, and also a preoccupation with betrayal. Gordimer's stories are seen as occupying a position firmly within the tradition of the modern short story. Her characteristic treatment of her material results in what this study sees as a typical Gordimer short story structure. The story starts with an introductory passage which presents the necessary background and characterisation, or sets the atmosphere. It then moves into a high focus during which a number of insights or revelations occur, which interact with each other to produce, at a higher level of abstraction, the central or unifying revelation which is the essence of the story. In these early stories, she shows a self-aware and self-regarding concern for questions of form. After Friday's Footprint, she devotes less attention to the formal qualities of stories, and gives more attention to questions of social and political comment. However, she does attempt some stories that could be labelled experimental short fiction, and she constantly explores the limits of the traditional artistic demands of the modern short story. After Not For Publication, she seems to turn her attention more towards longer works in order to find a suitable genre for her material. Her consistent use of critical realism, her special ability to capture the nuances and minutiae of experience and character are well suited to the short story form. This study shows the extent to which the short story serves as a vehicle for the expression of her perceptions of and interaction with her society as she develops from the pre-liberal to the committed radical writer and commentator on her society and its people.
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    The influence of low physical activity levels versus extreme physical activity levels on brain structure and working memory
    (2020) Paruk, Tasneem Yusuf; Jankiewicz, Marcin; Rauch, Laurie; King, Michael
    Background: Habitual levels of moderate to vigorous levels of physical activity (MVPA) levels are associated with positive health outcomes and improvement in cognitive function. A challenge facing optimal health outcomes is determining optimal levels of physical activity levels; people can engage in extreme sedentary or high levels of physical activity. For example, levels of low physical activity and participation in ultra-endurance events are increasing. However, the impact of extreme physical activity levels on brain matter volume and working memory is not well understood. This thesis thus investigated the relationship between different levels of MVPA, brain structure, and working memory. The aim of the thesis was to understand the relationship between large volumes of physical activity with global and regional brain matter volumes using brain imaging, and the impact of physical activity on cognitive function using the N-back task. The first part of the thesis examined how habitually high or low levels of MVPA differently impacted brain matter volume in healthy individuals. Whilst, the second part of the thesis investigated the differences in working memory between the low active and high active groups. Methods: Participants aged 20-59 years, were split into a High Activity (HA) group (N = 12, 27.9 ± 26.6 years) that exercised for > 9 hours of per week (MVPA > 540 minutes) and a Low Activity (LA) group (N = 9, 28.33 ± 11.192 years) that exercised < 2 hours (MVPA < 120 minutes). Total and regional brain matter volumes were measured using Magnetic Resonance Imaging (MRI) and analysed using Voxel-Based Morphometry (VBM). Habitual levels of physical activity were measured using the Global Physical Activity Questionnaire (GPAQ). For the second part of this thesis, we tested participants aged 20-59 years. Participants were split into a High Activity (HA) group (N = 6, 24.86 ± 4.67 years) that exercised for > 9 hours of per week (MVPA > 540 minutes) and a Low Activity (LA) group (N = 6, 30.14 ± 15.31 years) that exercised < 2 hours (MVPA < 120 minutes). Working memory was compared between the two groups using a PC-based N-back task. Results: The HA group had greater total brain matter and total white matter volumes vs. the LA group, and brain matter volumes were positively associated with increasing physical activity levels. However, the HA group had reduced regional brain volumes in the postcentral gyrus, middle frontal lobe, and the sub-lobar thalamus. HA and LA groups did not differ in working memory performance on the N-back task. Conclusion: Larger than normal amounts of weekly PA was associated with increased total brain matter and total white matter volumes, however, the volume of three regional brain areas were reduced.
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    The wild olive bowl
    (2014) King, Michael; Barris, Ken; Coovadia, Imraan
    Set against the political backdrop of the boycotts, arson and funerals of July 1980 in Grahamstown, this novel explores how the discovery of the dead body of a street child under the walls of St Jude’s Chapel sets events in motion that provoke the spiritual crises faced by the two protagonists. Father Philip Riley, the non-stipendiary curate at St Jude’s who had come to South Africa as a missionary inspired by Trevor Huddleston, has over the years lost any sense of his priestly vocation and his own personal beliefs. Lieutenant Daniel Broughton of the Grahamstown CID has to solve the mystery of the boy’s death, but he too has lost his idealism following a career in the South African Police that began at Sharpeville, and now hovers in a dead-end position in Grahamstown. Both these men have to come to terms with what the death of the street child requires of them. Riley has to overcome his reluctance to give the child a proper burial, and Broughton has to dig deeper than he is initially willing to, to determine how the child died. As the story unfolds, details emerge which thwart the opening attempts by both men to deflect any responsibility for the child from themselves. Riley had started life in an orphanage, and had been forced into colluding with the supervisor to cover up the cause of death of one of the orphans. He is challenged by the selfless love shown for the child by Mrs Mabata, a parishioner at St Jude’s who had tried to foster the street child. He realises that his reluctance to engage with the situation has to do with denying his own failures, based on his own life story. Giving in to pressure from a Roman Catholic priest to carry out the funeral, he discovers an inner strength to defy a police order not to conduct the funeral. The funeral goes ahead successfully, and Riley experiences moments of transcendence that allow him to re-discover his vocation. On the other hand, Broughton discovers that the street child’s involvement as an informer for the Security Police had been the cause of his death.